Contextual Match-making In Waste Biomaterials Management For Peri-urban Agriculture

Peri-urban agriculture is constrained by inadequate space and insufficient inputs. The objective of this paper was to estimate volumes of peri-urban agriculture waste materials generated and match it with identified users who need them in Kampala City (Uganda) as either animal feeds or manure. The mass of manure from animals and the crop residues generated were determined using the standard manure potential of animals and crop to residue (C:R) ratio methods respectively. The required baseline number of animals and crops grown in Kampala was obtained from secondary data. Of the 263,449 livestock animals in Kampala, a potential of 11,499 Mt of manure can be generated that can sustain 858 farmers each occupying 0.4 ha of land and using 13.33 Mt of manure each on their field. This manure when used as fertilizers for the common crops grown in Kampala (Maize, Bananas and Beans), it can meet nutrient requirements of 135 ha of maize or 99 ha of Bananas or 132 ha of beans. The potential crop residues from the major crops amount to 4,162 Mt and can meet nutrient requirements of 20,033 broiler chickens or 18,117 beef cattle or 18,237 pigs annually. Utilizing the bio wastes generated in Kampala as agriculture inputs can therefore be a remedy to the high costs of fertilizers and animal feeds as well as protecting the environment against gaseous emissions resulting from the poor disposal of these waste

Optimisation of eggshell-zeolite composite as a potential surfactant adsorbent for hand-washing wastewater

Surfactants present in handwashing wastewater impede performance of biological treatment processes. In this study, design expert software was used to optimise a composite adsorbent from eggshells and zeolite for removal of surfactants. Percentage of eggshells in the composite, calcination time and temperature were design parameters while chemical oxygen demand (COD) was indicator for surfactants. Optimal parameters were 31.6%, 1.4h and 310.9 °C for eggshells percentage, calcination time and temperature, respectively. Resultant adsorbent had methylene blue number, surface area, pore diameter and COD removal of 95mg/g, 26m2g−1, 10nm and 88%, respectively. These parameters and nitrogen adsorption/desorption isotherms confirm effective mesoporous structured adsorbent

Comparative Performance of Organic Fertilizers in Maize (Zea mays L.) Growth, Yield, and Economic Results

Maize is a major crop grown and consumed in Uganda and it requires a high fertilizer input. However, the existing inorganic fertilizers in the market are often not affordable especially to small scale farmers, which results in decreased maize yields in the country. On the other hand, there is an abundance of unutilized animal manure, which, when treated, can be used to increase maize yields. This study evaluated the response of maize to products of different cattle manure treatment methods as well as inorganic fertilizer. The treatments such as cattle manure stored under shade (T), cattle manure stored in the open (M), cattle manure slurry digestate (S), vermicompost (V), and an inorganic fertilizer, DAP (D) were all applied in completely randomized block plots at an equal application rate of 50 kg N ha−1 with four replications per treatment. Control plots (C) where no fertilizer was applied were also considered. The experiment was done for two planting seasons in 2018. Number of leaves, plant height, cob, and grain yields were used to evaluate the performance of different fertilizer treatments. Economic assessment of all the six treatments was also carried out to determine the economic viability of applying these fertilizers on maize. Maize growth parameters and yields were all significantly increased (p < 0.05) with an application of both organic and inorganic fertilizers when compared with the control. However, there was no significant difference (p > 0.05) in the maize yields under the different fertilizer treatments. Vermicomposting was the most economically viable manure treatment method due to low operating costs and higher returns on investment that are supplemented with the production of chicken fodder (earthworm biomass) and, thus, can be recommended to farmers for production of a fertilizer that increases maize yields with assurance of economic returns

Assessment of a Cattle Manure Vermicomposting System Using Material Flow Analysis : A Case Study from Uganda

Growth in cattle population is associated with increased manure generation whose current management in low-income countries is associated with health and environmental problems as well as low utilization rates. This trend can be reversed by promoting better manure management technologies. This study assessed vermicomposting as one of the technologies to manage organic wastes, using the case study in Uganda. A vermicomposting system using cattle manure and earthworms (Eudrilus euginea) was monitored for one year with the harvesting of products (compost, earthworm biomass) after every three months. Vermicompost samples from the beginning of the experiment and after every harvest were analyzed for the following parameters: pH, ash content, volatile and total solids, nutrients N, P, K, and C. Emissions of CO2, CH4, NH3, and N2O were also measured. Material flow analysis was used to determine the flows and retention of nutrients within the system. Results showed that total solids, ash, N, P, and K content significantly increased, while contents of volatile solids and C, as well as the pH, significantly decreased over time. Of the materials that entered the vermicomposting system, 46% went to vermicompost, 2% into earthworms, and 52% was lost to the atmosphere. Substance flow analysis showed that 30% of C went to vermicompost, 69% was emitted to the atmosphere, and 2% ended up in earthworms while 75% of N was transferred to vermicompost, 7% went to earthworms, and 18% escaped into the atmosphere. The cumulative emissions were 102 g CO2 kg−1 waste, 7.6 g CH4 kg−1 waste, and 3.943 × 10−5 g N2O kg−1 waste on a dry basis, while NH3 was not detected throughout the measurement time. Compared to other manure management methods, vermicomposting demonstrated good potential in conserving nutrients as well as reducing greenhouse gas emissions. View Full-TextAustrian Development Cooperation (ADC

Optimization of heavy metal removal by activated carbon obtained as a co-product from fast pyrolysis of rice husks

The realization of a circular economy calls for maximum utilization of existing resources with no recoverable waste after the process cycle. During fast pyrolysis of biomass to produce bio-oil for energy purposes, solid residues in form of bio-char are generated. In this study, residual char after pyrolytic-oil extraction from rice husks was activated using steam at 800 °C to produce activated carbon (AC). The formed AC was characterized and evaluated for removal of heavy metals from contaminated water. Box Behnken Design of Response Surface Methodology was used to optimize the removal of Cu2+, Co2+, Zn2+, Pb2+, and Ni2+ from water. The process conditions were: adsorbent dose (2–12 g/L), contact time (30–180 min) and temperature (25–70 °C). Characterization of AC revealed surface area and pore volume of 407 m2g-1 and 0.22 m3g-1, respectively. For all developed models, adsorbent dose, and contact time were the most significant terms. A linear model best fits Cu2+ remediation, while quadratic models best-fit removals of Co2+, Zn2+, Pb2+, and Ni 2+. Heavy metal removal efficiency increased with increasing adsorbent dose, contact time and temperature. Optimum treatment parameters were: adsorbent dose (11.90 g/L), contact time (172.5 min), temperature (54 °C) with removal efficiencies of 98.2%, 84.1%, 75.3%, 98.1%, 75.7% for Cu2+, Co2+, Zn2+, Pb2+, and Ni2+, respectively. Adsorption data best fitted Langmuir isotherm and pseudo second order models. These results confirm the applicability of AC from pyrolytic-oil residual char for adsorption of heavy metals. Use of AC from residual char in water treatment contributes to circular economy